When cellplanning a mobile telecommunication system, it is important to be able to register information about the traffic behaviour, i.e., it is important to be able to register traffic and measurement data that arrives from one or more mobile stations. When constructing a cell network, it is also important to be able to detect the presence of one or more mobiles in the vicinity of a border between two cells, in order to verify the earlier estimated radio coverage. It is also important to be able to study the intensity of the traffic in the cell when modifying the cell network, for instance, when wishing to divide a cell into two parts. Finally, it is often desirable to be able to study the behaviour of a given type of mobile, so as to enable a comparison to be made with other types of mobile stations, for instance.
WO 88/08238 discloses a method of registering mobile stations in a mobile telecommunication system and therewith determine the geographical location of the mobile. A method of registering traffic data from one or more mobile stations located within a group of cells controlled by a base station controller while a call is in progress is also known from GSM-recommendation 08.08. A message "trace invocation" is ordered by an order command in a switching central to be sent to the base station controller as soon as a call has been connected to the selected mobile station. Registration of traffic data from the mobile is commenced upon receipt of the "trace invocation" message by the base station controller, and the traffic data is stored in a database in the base station controller. The traffic data to be stored in the database has earlier been determined in response to a storage command in the base station controller and may have the frequency used by the mobile or when the mobile from one cell to another within the cell area controlled by the base station controller, i.e., when so-called inter-BSC-handover takes place. One problem with this known technique is that registration of traffic data ceases at the time the mobile leaves the cell area of the base station controller, i.e., after a so-called inter-BSC-handover. Another problem with this known technique is that when a storage command is preinserted in the base station controller, prior to having received the "trace invocation" command, it is necessary to determine the type of traffic data to be registered. This predetermined type of traffic data will then apply to traffic data from all selected mobile stations.